Abstract The tetrahalogenometallates CaHgBr4·8H2O, CaCdI4·8H2O and SrCdI4·8H2O which have been obtained by crystallization from aqueous solutions form different structures. The orthorhombic compounds CaHgBr4·8H2O (Cmca, a = 1720.1(6) pm, b = 1329.2(4) pm. c = 1369.5(7) pm, Z = 8, R =0.041) and SrCdI4·8H2O (Pnma, a = 1404.6(2) pm, b = 1841.1(5) pm. c = 1420.6(3) pm, Z = 8, R = 0.037) are built up from dodecahedral [A(H2O)8 ] cations (A = Ca, Sr) and tetrahedral MX4 anions (M = Hg, Cd) which are cubic closed packed in a CuAu type structure. The tetragonal structure of CaCdI4·8H2O (P4/nbm, a = 1268.14(13) pm, c = 536.96(35) pm. Z = 2, R = 0.034) contains antiprismatic [Ca(H2O)8]2+ cations and tetrahedral Cdl4 anions, which form together a tetragonal primitive rod package.